Mating System And Mating Compatibility Of Robinia Pseudoacacia L. During Controlled Pollination Without Castration

The large number of falling flowers and fruits caused by castration before pollination and cumbersome manual operation seriously affected the effect of controlled pollination on black locust(Robinia pseudoacacia L.).But hybrids produced by controlled pollination is the main source for obtaining the basic population of the next generation,which is of great significance for the genetic improvement of high-generation in forests.In order to explore the controlled pollination technology without castration,artificially controlled pollination and honeybee-controlled pollination were conducted on black locust without castration.Combined with the morphological observation and SSR paternity identification of the offspring at different developmental stages after controlled pollination without castration,the mating system of artificially controlled pollination and honey-bee controlled pollination without castration of black locust were analyzed.And the influence of the genetic relationship between the parents on the mating compatibility were studied.Meanwhile,the feasibility of artificially controlled pollination and honeybee-controlled pollination without castration was evaluated.The main findings and conclusions are as follows:(1)Analyzed the mating system of artificially controlled pollination of black locust.In the paternity analysis of offspring produced by artificially controlled pollination without castration from a total of 20 mating combinations in three consecutive years,the average outcrossing rate of the offspring produced by artificially controlled pollination without castration in the three years was 60.76%,60.02% and 50.43%,respectively.And there is no significant difference between the average outcrossing rates in each year.A total of 10 out of 20 mating combinations had outcrossing rates higher than self-crossing rates,and the overall outcrossing rate was 57.07%.Artificially controlled pollination without castration does not affect the generation of hybrids of black locust.The mating system of artificially controlled pollination without castration for black locust is a mixed mating system that can both self-cross and outcross.(2)Observed and analyzed the offspring selection phenomenon during the sexual reproduction of black locust.In the immature zygotic embryos at 30 d and mature seeds after artificially controlled pollination without castration on black locust,a great number of offspring were eliminated due to abortion.The results of paternity analysis showed that the aborted offspring in the immature zygotic embryos at30 d after pollination mainly came from outcrossing pollen,while the aborted mature seeds contained a great number of outcrossing and self-crossing offspring.(3)Clarified the influence of the genetic relationship between parents of black locust on mating compatibility.The correlation analysis of the genetic relationship between parents and the mating compatibility showed that in zygotic embryos at7d(p = 0.023 <0.05),in normally developing zygote embryos at 30d(p = 0.000 <0.01),and in mature seeds(p = 0.013 <0.05)after artificially controlled pollination without castration,the genetic relationship between parents was significantly related to the mating compatibility.The genetic relationship between parents of black locust will affect the mating compatibility.And the genetic relationship between parents of black locust has a greater effect on the development of zygotic embryo than that of pollen germination and insemination during reproduction.(4)Analyzed the mating system of honeybee-controlled pollination of black locust.The experimental system constructed by interception and grafting was used to conduct the experiment.Seeds were obtained from three female trees after honeybee-controlled pollination,and cultivated 174,18 and 84 offspring seedlings.The emergence rates were 37.26%,15.93% and 17.07%,respectively.The results of paternity analysis for all offspring seedlings showed that the outcrossing rates of the three offspring seedling populations were 95.40%,100.00% and 91.67%,respectively.The mating system of honeybee-controlled pollination without castration of black locust is the same as the natural open pollination state,which is a mating system based on outcrossing.(5)Obtained two full sibling family populations of black locust,and formulated a complete flow chart for honeybee-controlled pollination without castration of black locust.Through honeybee-controlled pollination,nursery and paternity identification,two full sibling family populations containing 91 and 75 black locusts were obtained.The flow chart for honeybee-controlled pollination without castration of black locust is to cover the nets,release bees,collect seeds,cultivate seedlings and other steps,and then combine with the identification of male parents to obtain hybrid offspring.(6)The feasibility of artificially-controlled pollination honeybee-controlled pollination without castration of black locust was evaluated.As far as the mating system of artificially-controlled pollination honeybee-controlled pollination without castration of black locust,it is feasible to carry out artificial or honeybee-controlled pollination of black locust without castration.However,in the artificially controlled pollination of black locust,the potential of outcrossing cannot be realized due to the large number of aborted outcrossing progeny.The problem of less seeds obtained in honeybee-controlled pollination without castration,and the low seed emergence rate requires more in-depth research and continuous optimization of experimental programs.